1. Field of the Invention
The present invention relates to an organic light emitting device.
2. Description of the Related Art
Organic light emitting devices are devices in which a plurality of organic light emitting elements are arranged in lines or in a matrix on a base material or a substrate. Organic light emitting devices can be used for multicolor display when organic light emitting elements are arranged so that one pixel (a set of sub-pixels) is formed from a combination of organic light emitting elements each emitting light of a different color, for example, a combination of one red-light emitting element, one green-light emitting element, and one blue-light emitting element.
Organic light emitting elements that form an organic light emitting device each include a pair of electrodes and an organic emission layer interposed between the pair of electrodes. The color of light emitted by an organic light emitting element varies depending on what material is selected as a light emitting material contained in the organic emission layer.
Vacuum vapor deposition using a metal mask is widely employed as a method of forming an organic compound layer and an upper electrode, which is formed on the organic compound layer. However, vacuum vapor deposition using a metal mask is low in the precision of the alignment of the metal mask with a substrate where a film is formed, and in the precision of film forming for reasons including the thermal expansion of the metal mask, and is accordingly unsuitable for the manufacture of a high-definition display device. In addition, portions of the organic compound layer and other films that are formed in regions at the edges of the metal mask decrease gently in thickness from around a set film thickness to 0, which means that the regions are non-effective regions and a waste in layout.
A method of selectively forming, with high precision, an organic compound layer by photolithography without using a high-definition metal mask is described in U.S. Pat. No. 5,953,585. Specifically, the method includes forming an organic compound layer, an upper electrode layer, and a protective layer on the entire substrate, and subsequently patterning the organic compound layer, the upper electrode layer, and the protective layer at once into a desired shape. The described method also includes performing separate patterning on the combination of “the organic compound layer, the upper electrode layer, and the protective layer” in regions that corresponds to three colors, R, G, and B, as needed.
However, ends of a film that is patterned by the method of U.S. Pat. No. 5,953,585, namely, photolithography, to be turned into the organic compound layer are exposed to the external environment. With the ends of the film to be turned into the organic compound layer exposed to the external environment, the very organic compound layer, which does not have gas barrier properties, deteriorates due to water and oxygen seeping from the exposed ends. Another problem of U.S. Pat. No. 5,953,585, which includes patterning the organic compound layer and the upper electrode layer but does not disclose how to form connection between an upper electrode and a feeding pad portion formed on the substrate side, is a possibility of failure to establish electrical connection to organic light emitting elements that form a device.